We've been using 3AN Bulkheads for 20 years and the standard offerings have their flaws. The biggest being too small of a mounting surface on the bulkhead side and the other being the bulkhead nuts are flat (not flanged) and too thin. This makes the nut hard to tighten, its scars up the surface, and without the flange it's not getting secured down as well.
We finally designed our own and the results have been great! Our bulkheads aren't regularly loosening and they just look better! Cut from 6061 Aluminum with Mil-Spec tolerances and anodized Chase Bays signature semi-gloss black.
This is for the 3AN Straight Bulkhead that INCLUDES Bulkhead Nut.